Process for producing cable oils by sequential refining steps



United States Patent O US. Cl. 208-14 Claims ABSTRACT OF THE DISCLOSURE Low ADF, 3000-8000 SUS (at 100 F.) cable oils are prepared from naphthenic lube fractions which have been acid-treated (e.g., S0 HF, H 80 neutralized, hydrorefined at 550-750 F. and 800-3000 p.s.i. of hydrogen and contacted with an adsorbent comprising bauxite or a naturally-occurring fullers earth bleaching clay, such as attapulgite.

CROSS REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of US. Ser. No. 622,398 of Ivor W. Mills and Glenn R. Dimeler, entitled Clay Treatment of Hydrorefined Cable Oils, which was filed Mar. 13, 1967 and is assigned to the Sun Oil Company, to whom the subject application is also assigned.

BACKGROUND OF THE INVENTION Although some cable oils are produced by synthesis, as by the polymerization of butenes, the more satisfactory cable oils are produced by refining selected fractions of naphthenic crude oils. Despite the very low ASTM D1934 initial (IDF) and aged (with copper for 96 hours at 115 C.) dissipation factors (ADP) of the polybutene cable oils (ADF in the order of 0.005), they suffer from the disadvantages, when compared to refined naphthenic oils, of increased volatility, thermal instability, oxidation instability, and poor electrical properties (e.g., a high power factor) in a closed-system oxidation test. The polybutene cable oils also contain reactive olefins and traces of chlorine, which are undesirable components in cable oils, and develop considerable acidity and increase in viscosity on PFVO aging.

It has also been found that cables containing polybutene oils are not superior in electrical characteristics to those cables containing properly refined naphthenic oils, thus showing that a low dissipation factor is not the sole criterion for a cable oil. However, due to the market appeal of a low ADF, the petroleum refiner is actively seeking means of further lowering the A'DF of present naphthenic cable oils (0.04-0.10) which are conventionally refined from naphthenic distillates by solvent extraction (as with furfural) followed by treating with sulfuric acid and clay contacting. Illustrative of such processing are British Patent Nos. 536,863 and 946,540. Preferably the naphthenic distillates have been caustic treated, for example, as by the processes disclosed in the following US. Patents: 2,770,580; 2,795,532; 2,944,014; 2,966,456; 3,080,312.

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SUMMARY OF THE INVENTION We have discovered a process of refining a naphthenic distillate oil to produce a cable oil having an ASTM D1934 ADF below 0.0035 and at least as low as the ADF of a polybutene cable oil having the same viscosity at 100 F. Our process comprises contacting the naphthenic distillate with an inorganic Lewis acid which is capable of extracting polar compounds from the distillate, allowing the resultant sludge to settle to produce an acidic oil layer, treating the acidic oil layer (as with a base and and/or an adsorbent and/or washing) to provide a neutral oil, hydrorefining the neutral oil to produce a hydrorefined oil having an ultraviolet adsorptivity at 260 mM. which is at least 40 percent (preferably at least 60 percent) less than that of the naphthenic distillate. In order to insure a low IDF, the hydrorefined oil is treated with an adsorbent comprising bauxite or a naturally-occurring fullers earth bleaching clay.

In our copending application, Serial No. 622,398, we have disclosed that superior cable oils can be produced from naphthenic lube oil fractions by severe hydrorefining followed by contacting with an adsorbent, such as clay. In the case of the high viscosity cable oils (4000- 6000 SUS at 100 F.), the type of clay used and the dosage of clay have no critical effect on the aged dissipation factor (ADF) of the resulting oil and the preferred adsorbent is a relatively inexpensive naturallyoccurring fullers earth bleaching clay, such as attapulgite. We also disclosed the surprising finding that with the lower viscosity cable oils (500-2000 SUS), both the nature of the clay and the clay dosage are critical if one wishes to obtain a cable oil having an A'DF below 0.010, that is, which approaches that of the synthetic polyolefin cable oils, such as the polybutene oils.

We further disclosed that sulfuric acid treating of the severely hydrogenated 500-2000 SUIS naphthenic oils, prior to clay contacting, does not sufliciently improve the ADF to warrant the expense of such additional treatment and that, with the higher viscosity cable oils (e.g. 4000- 6000 SUIS) such H treatment of the hydrorefined oils prior to clay contacting can actually be detrimental in that the resulting refined oil can have a larger ADF than a similarly hydrogenated oil which is refined by clay contacting alone.

The present application detals with our unexpected finding that if a naphthenic distillate oil is acid treated (as with H 80 and neutralized prior to severe hydrogenation and clay contacting, the resulting refined naphthenic oil is novel in that it has an ADF as low as those of the polyolefin oils, such as the polybutene oils, which have heretofore had much lower ADFs than were obtainable from refined naphthenic oils. This novel oil is especially useful as an insulating fluid in electrical cables carrying greater than 500 kv. Such an insulating fluid can contain the usual inhibitors and from 10-90 volume percent based on the napthenic cable oil, of polybutene cable oil.

Our finding that there is an unexpected advantage to this process sequence for the production of electrical oils is to be compared with the teachings of U..S. 2,973,- 317 which discloses that acid treatment after hydrogenation of a 1600 SUS (at F.) naphthenic distillate produces higher yields of lube oils than does the reverse procedure (acid treatment prior to hydrogenation).

Our discovery is distiguished from the process of U.S. 2,973,315, wherein naphthenic distillate having a viscosity at 100 F. of 1594 SUS is contacted with 32 lbs./ bbl. of 98 percent H 80 allowed to settle, separated from the resulting sludge, and the resulting acidic oil, having an acid number of 1.34, is subjected to hydrogenation at 700 F. and 500 p.s.i.g. to produce a lube oil having a gigcosity of 802 SUS at 100 F. and an acid number of In the process of U.S. 2,973,315, the H 80 treated oil is not neutralized prior to hydrogenation and no clay contacting isused. In contrast, in our process, in order to obtain a cable oil having an ADF less than 0.0035, neutralization, preferably with basic salt, to an ASTM D974 acid number'less than 0.1, preferably less than 0.05, is an essential step prior to hydrorefining since this improves the severity of the hydrogenation, 'as measured by the decrease of ultraviolet absorptivity in the 260 mM. region (260 UVA). In the process of U.S. 2,973,315, the dissolved acidic components rapidly reduce the activity of the hydrogenation catalyst. Clay contacting is also necessary for the production of our novel cable oil because it insures that the IDF will be below 0.001.

Also to be distinguished is the method of U.S. 2,944,015 wherein a naphthenic lube fraction having a viscosity at 100 F. of from 50-6000 SUS is acid-treated with 5-10 lbs./bbl. of H 50 the resulting acid oil neutralized with soda ash solution, and then hydrogenated at 450- 700 F. and 400-700 p.s.i.g. In this method, from 5-30 s.c.f. of hydrogen are reacted per barrel of oil to improve the color, color stability, and oxidation stability of the oil. This process is similar to that of the present application except that it utilizes a mild hydrogenation procedure (or hydrotreatment) which is not sufficiently severe to reduce the 260 UVA of a naphthenic distillate oil by at least 40 percent. In our process the hydrogen consumption is greater than 100 s.c.f./bbl. (usually 200-400 s.c.f./bbl.) and the hydrogen pressure must be at least 800 p.s.i.g. (preferably above 1000 p.s.i.g.) in order to reduce the 260 UVA of a naphthenic distillate by at least 40 percent (preferably more than 60 percent).

DESCRIPTION OF THE INVENTION The base oils which are hydrorefined are obtained, for example, by vacuum distillation (as in U.S. 3,184,396) of naphthenic crude oils (which preferably are substantially free of naphthenic acids). Usually (to maintain a high viscosity and/ or a high flash point) materials boiling below about 600 F. are removed from the hydrorefined oils, as by atmospheric distillation, prior to clay contacting.

By hydrorefining, We refer to processes conducted in the presence of a hydrogenation catalyst at from about 550-750 F. and from 800-3000 p.s.i. of hydrogen partial pressure at a liquid hourly space velocity of from 0.2-8.0, preferably conducted either in vapor phase or trickle phase. Product recycle, for example, as in U.S. 2,900,433, can be used, preferably at a product to fresh feed ratio below 10:1 (more preferably 8:1 to 1:1).

Preferably the temperature is below that at which substantial cracking occurs; that is, no more than 20 weight percent (preferably less than 10%) of the feed stock is converted to material boiling below 300 F. Although the maximum hydrogenation temperature which willnot produce substantail cracking is somewhat dependent upon the space velocity, the type of catalyst and the pressure, generally'it is below 750 F. We prefer to operate below 700 F., more preferably below 675 F. At total pressures below 2000 p.s.i.g. we prefer atemperature no greater decreases appreciably, higher temperatures (c.a. 675 F.) than 650 F. since above that temperature (with a fairly fresh catalyst) the production'of low boiling material and the degradation of oil viscosity become substantial. Afte some months of us if the activit of he cata y I v 1 I can be used to prolong catalyst life, i.e., to delay regeneration or replacement of the catalyst.

We further prefer to operate at conditions such that hydroaromatization is not a dominant reaction. That is, the temperature, pressure, liquid hourly space velocity (LHSV) and hydrogen recycle rate should be chosen such that the gel aromatic content of the resulting hydrorefined oil is not greater than that of the base oil after acid treatment (i.e., the neutral oil).

For example, at a fresh feed LHSV of 0.2-1.0 and recycle LHSV of 2-5, with sulfided nickel-molybdenum oxides as the catalyst, hydroaromatization will be observed at about 750 F. at hydrogen partial pressures below about 150.0 p.s.i. if there is no hydrogen recycle. If the hydrogen recycle is about 4000 sci/minute, hydroaromatization will not dominate at the same temperature unless the total hydrogen pressure is below about 1000 p.s.i.

Such avoidance of hydrocracking and hydroaromatization in the production of cable oils by the present invention is to be contrasted with our discovery that in the production of transformer. oils from a 40-70 SUS (at 100, F.) naphthenic distillate oil by hydrorefining, it is advantageous to choose conditions (e.g., 625 F., 1200 p.s.i.g. of H such that the sulfur and nitrogen contents of the oil are substantially reduced with a resulting partial saturation of polycyclic aromatic hydrocarbons such that the ultraviolet absorptivity at 335 millimicrons (335 UVA) is below 0.04 (preferably below 0.01). However, the electrical properties of the resulting transformer oil on aging are improved if the sorefined oil is subjected to hydroaromatization and/or hydrocracking conditions (usually, at 1000-1500 p.s.i.g. and a temperature above 675 F.) for a suflicient time to increase the content of tetracyclic and higher aromatic hydrocarbons such that the 335 UVA of the resulting refined oil is from 0.05 to 0.5. After adsorbent contacting, the resulting transformer oils can have a sludge-free Doble life of at least 64 hours (typically over hours).

Typical of such severe hydrorefining methods, which can be used in our process when conducted within the aforementioned processing conditions, are those of U.S. 2,968,614; 2,993,855; 3,012,963; 3,114,701; 3,144,404; and 3,278,420.

Typical catalysts are molybdenum oxide, cobalt-molybdenum oxides, nickel-molybdenum oxides, cobalt-nickel molybdenum oxides and tungsten-nickel molybdenum oxides, preferably presulfided and on a carrier such as silica, alumina, alumina-titania and alumino-silicates (either crystalline or amorphous). Nickel sulfide, nickelmolybdenum sulfide, tungsten disulfide, nickel-tungsten sulfide and molybdenum disulfide, per se or on a carrier, can also be used as catalysts. Examples of operable catalysts are those of U.S. 2,744,052; 2,758,957; 3,053,760; 3,182,016; 3,205,165; 3,227,646; and 3,264,211.

I We prefer that such hydrorefining (or severe'hydrogenation) be a trickle phase process (although gas phase operation with hydrogen recycle up to 12,000 s.c.f./b. can be utilized) at 575675 F. and 900-1500 p.s.i. of hydrogen partial pressure using a catalyst comprising nickel and molybdenum sulfides on alumina or silica. Usually a cobalt-molybdenum catalyst will require 25- 100 percent greater hydrogen pressure, at a given tem perature, recycle and LHSV, to produce a cable oil comparable to that obtained with a sulfided nickel-molybdenum catalyst.

As has been noted in U.S. 2,973,315, the severity of hydrogenation can be measured by the hydrogen consumption; however, with cable oils we prefer to follow severity by observing the decrease in ultraviolet absorptivity in the 260 millimicron region. That is, due to hydrogenation of polycyclic aromatic hydrocarbons, the resu-ltinghydrogenated oil will have lower ultraviolet adsorptivity in the 260 millimicron region than will the base oil before hydrogenation. Typically, after severe. hydrogenation, the 260 mM. adsorptivity is less than 7.5

for a 4000-6000 SUS naphthenic distillate oil, less than 6 for 900-3000 SUS oil, and less than 4.5 for a 300-800 SUS oil. Preferably, in the 3000-8000 SUS range, the hydrogenated oil will contain less than 0.2% sulfur and less than ,500 ppm. of nitrogen. The ADF of the higher viscosity (above 4000 SUS) severely hydrorefined oils will be less than 0.010 but the lower viscosity (below 1000 SUS), severely hydrorefined oils Will have ADFs above 0.015, typically above 0.020. Due to differences in aromatic, sulfur and nitrogen content of the base oils, hydrogen consumption can vary greatly; however, usually hydrogen consumption for a naphthenic acid-free distillate is at least 150 s.c.f./bbl. (typically about 300 s.c.f./bbl.).

A cause of such hydrogen consumption is that we pre fer to hydrorefine at conditions (e.g., 575-650 F., 900- 1500 p.s.i.g. of 100% H no gas recycle, sulfided Ni-Mo catalyst) such that the total gel aromatics in the feed to the hydrorefining step are reduced by about 5 to 25% (mainly due to removal of polar compounds) and most (55-90%) of the dicyclic and higher aromatics in the feed are converted to monocyclic aromatics.

In contrast, mild hydrogenation processes frequently consume less than 150 s.c.f. of H /bbl. and are characterized by little change in polycyclic aromatic content of the oil. Mil-d hydrogenation is frequently termed hydrotreating and is usually conducted below 800 p.s.i. of hydrogen or below 550" F. Typical of mild hydrogenation treatment are US 2,865,849; 2,921,025; 2,944,015; and 3,011,972.

Under hydrorefining conditions of equal severity, our acid-treated neutral oil will consume somewhat less hydrogen than the parent distillate from which it is obtained. Such a hydrorefined, acid-treated oil will have a lower ADF, a lower 260 UVA (at least 30% lower) and contain les sulfur, nitrogen and polar compounds than will the parent naphthenic distillate after hydrorefining with the same catalyst at the same conditions of temperature, pressure, LHSV, and gas recycle. Adsorbent contact with bauxite or attapulgite will improve the ADF and lower the nitrogen and sulfur content of such hydrorefined oils;

however, even after such contacting, the hydrorefined oils;

acid-treated oil will have a significantly lower ADF than will the parent oil after the same contacting.

The acid treatment of the oil can be by any conventional process utilizing an inorganic Lewis acid Which is capable of extracting polar compounds from the oil and so long as the separation of the resultant sludge (or extract) and residual acidic material from the oil is substantially complete after neutralization. The acid treatment is preferablywith -60 lbs./bbl. of 93120*% H 80 and can be by processes such as those of US. 2,279,461 and US. 2,282,033. Although concentrated H 80 is the preferred acid, other acids can be used, such as oleum or S0 (see US. 2,908,638), chlorosulfuric acid, HF, AlCl B1 HF-BF SbCl SbCl etc.

In general, the naphthenic distillate, which may be diluted with an inert, less viscous solvent, is mixed with the Lewis acid. Two phases form, an oil phase and an acid phase which is insoluble in the oil phase and which contains components extracted from the naphthenic distillate. The oil phase will comprise unextracted components of the parent distillate and dissolved acidic material. The oil phase 'is separated from the acid phase and is contacted with an adsorbent for the acidic material and/or mixed a C -C aliphatic aldehyde, a C -C aliphatic ketone or mixtures thereof. To maintain catalyst activity and, thus, obtain sufiicient severity of the hydrorefining, the acidity of the neutralized oil must be less than 0.05 mg. KOH per gram of oil (preferably 0.00)

HF treatment (5-50 percent by weight of the oil) at 30200 -F. possesses the advantage of removing undesirable nitrogen, sulfur and oxygen-containing polar aromatic compounds from the oil but not the desirable aromatic hydrocarbons. Dilution (0.5 to 5 volumes of solvent per volume of oil) with a lower boiling (below 350 F.), inert (will not react with the acid), less viscous solvent (below 30 SUS at R), such as naphtha, benzene, isooctane, aviation alkylate, or n-heptane, etc. can be used to improve contact (by decreasing solution viscosity) at the lower temperatures (e.g. 0-90 F.). The pressure used is preferably such that the HP, at the temperature employed, is in the liquid phase. Neutralization of the acidic oil remaining after sludge removal can be by washing, distillation, or by adsorbent treatment (as with bauxite or clay) or by a combination thereof.

A single treatment with hydrogen fluoride may be employed, or a plurality of treatments with hydrogen fluoride with separations of sludge between treatments. In the latter manner of operation, a smaller total amount of hydrogen fluoride generally is required to obtain a given degree of treatment than in the case of a single treating stage.

The sludge obtained from such HF treatment differs from the sludge obtained from H 50 treatment of a petroleum distillate in that the reaction of the HF and the polar aromatics is readily reversible and S, N, and 0 compounds of the sludge can be recovered therefrom by distilling the sludge to remove (and recover) HP. The so-recovered S, N, and 0 compounds appear to be essentially the same as those present in the original oil charge.

In contrast it is very diflicult and expensive to recover acid from H SO -sludge and such recovery methods (as by pyrolysis) destroy or greatly alter the organic portion of the sludge.

Despite the advantages of HF for such acid-refining, H 50 will usually be the acid chosen by the refiner.

It is sometimes advantageous to use solvent extraction prior to such acid-treating. In this embodiment, any of the well known selective solvents for aromatics can be employed, e.g., furfural, phenol, sulfur dioxide, nitrobenzene, B,B-dichloroethyl ether, etc. Temperatures of 100-250 F. and solvent-to-oil ratios of 14:1 are preferred. Extract yield is usually 10 to 30 weight percent of charge. Other conditions and yields are contemplated in some cases. Highly aromatic, non-discoloring rub-her process oils (e.g., 45-90% aromatics) can be prepared from such extracts by a sufliciently severe acid-treatment to reduce the polar aromatic content of the product oil to less than 3 percent or by hydrorefining under conditions such that the aromatic content of the oil is essentially maintained, or is increased (as by hydroaromatization).

Frequently a combination of solvent extraction and acid-treatment is less expensive than the use of acid treatment alone to produce a neutral oil of given aromaticity and polar content, because the more aromatic oil recovered from a solvent extract has a better market value than the residue from acid refining. For example, solvent extraction can generally be used to decrease acid consumption by about 50%. Such a combined process allows the production (from the raffinate) of a less polar oil of given aromatic content than can be produced solely by extraction with an aromatic selective solvent, such as furfural, S 0 or phenol.

Solvent extraction, however, cannot be a complete substitute for acid-treatment since it is characteristic of extraction with an aromatic selective solvent (within the ranges of temperature and solvent-to-oil ratio practiced by the prior art) that the solvent extracts the desirable aromatic hydrocarbons along with the undesirable polar aromatic compounds. After a given degree of aromatic removal has been obtained by solvent extraction, further extraction results in a more selective removal of the desirable aromatic hydrocarbons from the raffinate and the relative polar aromatic content of the refined raffinate oil will not decrease. In fact, in such a deeper raffinate, the ratio of polar aromatics to total aromatics can increase.

For example, furfural extraction of a 2400 SUS (at 100 F.) distillate containing 47.5% aromatics (260 UVA of 11) and 2.7% polar compounds can produce a 1200 SUS oil containing 31.6% aromatics (260 UVA of 2.5) and 1.5% polar compounds. A second extraction of this product (or a more deep initial extraction of the distillate) produces a 1000 SUS oil containing 22.5% aromatics (260 UVA of 1.0) and 1.0% polar aromatics.

In contrast, when the 31.6% aromatic content rafiinate is treated with 10 lbs. of HF per 100 lbs. of oil, the resulting neutral oil contains 31.2% aromatics and 0.5% polar compounds. When this acid-treated, furfural rafiinate is hydrorefined and contacted with bauxite, the resulting cable oil has an ADF that is at least as low as those exhibited by commercially available polybutene oils of the same viscosity.

Similarly, when a furfural raffinate of an SOD-12,000 SUS naphthenic distillate is further treated with a sulfonating agent (e.g., S H 80 oleum, chlorosulfonic acid) in an amount equivalent to from 3-40 lbs. of S0 per barrel (preferably 30 lbs./b-bl.) or with 10-40 lbs. of HF per 100 lbs. of oil, the resulting neutralized oil will have a lower ratio of polar aromatics than did the untreated raffinate, and after hydrorefining and adsorbent contacting, the resulting cable oil will have an ADF at least as low as that of a polybutene oil of the same viscosity.

The treatment of the oil with an adsorbent can be by the usual methods, such as by percolation of the oil through a bed of the adsorbent material at temperatures sufficiently high to allow a reasonable rate of flow through the bed or by contact filtration (or slurry and filtration) in which procedure the oil is mixed with finely divided adsorbent to form a slurry and the mixture is filtered in a conventional manner. In either method the oil can be diluted with a less viscous, non-reactive solvent, such as alkylate, to decrease contact time and/or to increase filtration rates. Such conventional processing is illustrated by the methods of U.S. 2,781,301; 2,596,942; and 2,346,127.

To reduce adsorbent consumption when contacting below about 200 F. the adsorbent admixtures should be substantially free of uncombined water; therefore, the usual commercially available clays (which can contain large amounts of water) should be dried, as in an oven, or preferably activated by such well known procedures as roasting.

The preferred adsorbents are bauxite and those clays which consist principally of the mineral attapulgite; however, we can use any naturally-occurring fullers earth bleaching clay'including adsorbent admixtures.

ILLUSTRATIVE EXAMPLES In the following examples, Example I illustrates the .severe hydrorefining of a highly viscous naphthenic lube severely hydrogenated cable oil is still 2.7 times greater than that of a commercially available polybutene oil of the same viscosity. Example II shows that when the severely hydrogenated cable oil is contacted with attapulgite, there is a 25% decrease in the, ADF. Example III shows that sulfuric acid treatment of the severely hydrogenated cable oil, followed by neutralization and contacting with attapulgite, is detrimental to the ADF, that is, the ADF of this oil is 44% greater than that of the clay contacted oil of Example II. Example IV shows the surprising results obtained when the naphthenic lubev fraction is H SO -treated and neutralized prior to the severe hydrogenation and clay contacting. That is, the resulting refined oil is novel and has an ADF equivalent to that of a polybutene cable oil of comparable viscosity. Note that the oil of Example III, which is H SO treated after hydrorefining, has an ADF which is 6.3 times the ADF of the oil of Example IV.

In the examples, percentages are by weight, all ultraviolet absorbency (UVA) measurements are at 260 millimicrons and all viscosity measurements are at 100 F., unless otherwise noted. Barrels are equal to 42 U.S. gallons. Products boiling below 400 F. (in each example less than 3 volume percent) are removed by distillation from the hydrorefined oil to raise the flash point to 450 F. or above.

EXAMPLE I A 5000 SUS naphthenic oil containing 40.2 aromatic hydrocarbons, 8.7% polar compounds (ASTM D2007), (i.e., 48.9% total gel aromatics), 0.38% S, less than 0.0% of naphthenic acids and having an ultraviolet absorptivity of 12.8 in the 260 millimicron region is obtained by the caustic distillation process described in U.S. 3,184,396, from a naphthenic crude blend having a viscosity-gravityconstant of 0.890. This 5000 SUS oil is hydrorefined at 600 F., at 1000 p.s.i. of hydrogen (1200 p.s.i.g. total pressure) using sulfided nickel-molybdenum oxides on alumina (3% NiO, 15% M00 and 82% Al O -presulfided to a sulfur content of 5%) as the catalyst, until the UVA is 6.3. The IDF of this severely hydrorefined oil is 0.0008 and the ADF is 0.0076. It contains 40.7% aromatic hydrocarbons, 5.2% polar compounds, 0% asphaltenes, 250 p.p.m. of nitrogen, 0.09% of combined sulfur and no detectable free sulfur.

Conventional refining of the 5000 SUS caustic distilled parent naphthenic oil, by furfural extraction, treating the resulting 85% raftinate with 20 lbs./bbl. of 99% H SO neutralizing and washing (utilizing the procedures of U.S. 2,973,317), followed by contacting the resulting neutral oil with 15 lbs./bbl. of attapulgite clay, produces a cable oil, containing 0.16% sulfur and having an IDF of 0.0034 and an ADF of 0.0357, which is 4.7 times the ADF of the hydrorefined oil of this Example I.

EXAMPLE II v The 0.0076 ADF hydrorefined oil of Example I is heated to 220 F 'then 15 lbs./bbl. of attapulgite is added, with mixing, to form a clay-oil slurry. The attapulgite has a pH of 7.5 (in 10% aqueous suspension) and is an aluminum-magnesium silicate containing 20.1% volatile matter (i.e., removable by heating for 20'minutes at 1700 F.). When heated at 200 F. for one hour the weight loss is 13.3%. The volatile-free clay analyzes 69.9% SiO 12.4% A1 0 11.2% 'MgO, 4.1% Fe O and 2.2% CaO. Its apparent bulk density is 32 lbs/cu. ft. and it has particles sized such that will pass through a 200 mesh screen.

After 20 minutes of clay/oil contact at 220 F., the clay is separated from the oil by filtration. The resulting refined cable oil has an IDF of 0.0004 and an ADF of 0.0057 (which is 25%. less than that of the hydrorefined oil) and contains 0.07% sulfur. A commercially available polybutene cable oil of substantially the same viscosity has an ADF of 0.0021. Therefore, although either the hydrorefined oil of Example I or the hydrorefined, clay-contacted oil of this Example II has a commercially acceptable ADF, the ADF of even the clay-contacted oil is nearly three times that of the polybutene oil.

Similar results are obtained when the amount of attapulgite used is Within the range of 3 lbs./bbl. of 25 lbs./bbl.

An increase in ADF (or, at best, no improvement) over the attapulgite is observed when the adsorbent used is from -20 lbs/bbl. of acid-activated clay or -25 lbs./ bbl. of a 1:1 by weight mixture of attapulgite and acidactivated clay. When the adsorbent is 10 lbs/bbl. of acidactivated clay, the resulting refined oil has an ADF of 0.010, which is a 22% increase over that of the hydrorefined oil of Example I.

EXAMPLE III The 0.0076 ADF hydrorefined oil of Example I is treated with 20 lbs/bbl. of 99% H 50 neutralized and washed, utilizing the procedures of US. 2,973,317, and then contacted with lbs/bbl. attapulgite. The resulting refined oil has an IDF of 0.0017 and an ADF of 0.0082, which is 44% greater than that of the clay-contacted oil of Example II. Note that this ADF is' higher than when the H 50 treatment, neutralization, washing, and clay contacting are omitted.

EXAMPLE IV The 5000 SUS naphthenic fraction of Example I is treated with 40 lbs/bbl. of 99% H SO' at 130 F., the resulting mixture allowed to settle, the sludge removed, the acidic oil neutralized and washed, as in Example III, to produce a neutral oil having an acidity equal to less than 0.01 mg. KOH per gram (ASTM D974) and containing 38.1% total gel aromatics (i.e., polar compounds plus aromatic hydrocarbons). The resulting H 80 treated, neutralized naphthenic oil (having a 260 UVA of 5.5) is then hydrorefined in the same manner as the oil of ExampleI. When this severely hydrogenated oil is contacted with 15 lbs/bbl. of attapulgite, the resulting refined cable oil has a 260 UVA of 2.1, an IDF of 0.0002 and an ADF of 0.0013 and contains 34.3% gel aromatics. Note that the oil of Example III has an ADF which is 6.3 times the ADF of the oil of this example.

The novel cable oil of this example is illustrative of the novel naphthenic cable oils which can be produced by our process containing 30-50 percent aromatics and having a viscosity in the range of 3000-8000 SUS at 100 F., an ADF less than 0.0025 in the absence of added oxidation inhibitors, an initial dissipation factor less than 0.001, an initial ASTM color less than 1.5, an aged A'STM color less than 2.0 and a 260 UVA less than 6.0. This oil is also representative of a more preferred class of such novel cable oils, which are particularly useful as a component (especially as the major component) of insulating fluids of electrical cables capable of carrying current at voltages of 500 kv. or greater, said novel cable oil containing 30-40% aromatics, less than 4% polar compounds, and having a viscosity of 4000-6000 SUS at 100 F., a 260 UVA less than 3.0, an IDF less than 0.0003, and an ADF less than 0.0015.

Substantially the same results are obtained when the naphthenic distillate oil is extracted with an aromatic selective solvent and the resulting rafiinate is treated with a smaller quantity of sulfuric acid. For example, a cable oil equivalent in ADF to that of Example IV is obtained by extracting the 5000 SUS distillate with 'furfural and contacting the resulting 85% raffinate (44% aromatics) with lbs/bbl. of 99% H 80 at 130 F., the sludge removed, and the resulting H SO -treated, fur'fural raffinate is neutralized, severely hydrogenated, and finally contacted with clay, as in Example IV.

Since such solvent extraction decreases the acid consumption such an additional solvent extraction can be less costly than the cost of this extra acid.

Electrical cables can be fabricated containing the usual oxidation inhibitors (e.-g., see US. 3,145,258) and viscosity modifiers, such as waxes (see US. 2,914,429) and containing, as an insulating medium, any of the novel oils disclosed herein or mixtures of such oils. Chelating agents, such as the Schiff base additives of US. 3,094,583,

can also be incorporated in cables containing our novel oils. Such electrical cables, containing our novel oils, possess exceptionally good aging properties.

In addition to parent application Ser. No. 622,398 (now U.S. Patent 3,462,358), the following later filed copendin-g applications, assigned to the Sun Oil Company, are related to the disclosure of the present application and contain a specific reference incorporating this disclosure therein: Ser. No. 730,999, filed May 22, 1968, Hydrorefined Transformer Oil and Process of Manufacture- Ivor W. Mills, Glenn R. Dimele-r; Ser. No. 812,516, filed Feb. 19, 1969, Catalytic Hydrofini-shing of Petroleum Distillates in the Lubricating Oil Boiling Range-Ivor W. Mills, Glenn R. Dimeler, Merritt C. Kirk, Jr., Albert T. Olenzak; Ser. No. 850,716, filed Aug. 18, 1969, Blended Hydrocarbon Oil and Process of Manufacture-Ivor W. Mills and Glenn R. Dimeler; Ser. No. 850,717, filed Aug. 18, 1969; Hydrorefined Lu b Oil and Process of Manufacture-Ivor W. Mills and Glenn R. Dimeler; Ser. No. 850,778, filed Aug. 18, 1969, Process For Preparing High Viscosity Hydrorefined Cable Oil-Iv0r W. Mills, Glenn R. Dimeler, William A. Atkinson, Jr. and James P. Hoffman; Ser. No. 850,779, filed Aug. 18, 1969, Electrical Conduit Containing Hydrorefined Oil-Ivor W. Mills, Glenn R. Dimeler and John J. Melchiore; filed on or about Oct. 25, 1969, Light-colored Highly Aromatic Oil and Process of Preparation-Ivor W. Mills, Glenn R. Dimeler and Merritt C. Kirk, Jr.; file-d on or about Oct. 31, 1969, Oil and Process of Manufacture of Blended Hydrorefined Oil Ivor W. Mills and Glenn R. Dimeler.

What is claimed is:

11. Process of refining a naphthenic distillate oil boil-ing mainly above 600 F. to produce a cable oil having an ASTM D1934 aged dissipation factor (ADF) below 0.0035, said process comprising contacting a charge stock consisting essential-1y of a straight-run naphthenic dis tillate or of a straight-run naphthenic distillate which is substantially free of naphthenic acids with concentrated sulfuric acid, S0 or HF, allowing the resultant sludge to settle to produce an acidic oil layer, treating said acidic oil layer to provide a neutral oi'l, hydrorefining said neutral oil to produce a hydrorefined oil having an ultraviolet absorpti-vity at 260 millimicrons (260 UVA) at least 40 percent less than that of said naphthenic distillate, treating said hydrorefined oil with an adsorbent comprising bauxite or a naturally-occurring fullers earth bleaching clay and recovering an oil having an ADF below 0.0035.

2. Process according to claim 1 wherein said naphthenic distillate oil is extracted with an aromatic selective solvent and wherein the raflinate from said extraction is subjected to said contacting with concentrated sulfuric acid, S0 or HP.

3. Proces according to claim 1 wherein said contacting is effected at a temperature of from 090" F. and in the presence of an inert solvent for said distill-ate, said solvent having a viscosity below 30 SUS at F. and boiling below 350 F.

4. Process according to claim 1 wherein said naphthenic distillate has a viscosity of 3000-8000 SUS at 100 F. and wherein said contacting is at a temperature from 0l40 F. with from 10-60 lbs/bbl. of 93-120 percent sulfuric acid, and wherein said acidic oil layer is treated with 'a base and washed with water, a C to C aliphatic alcohol, a C to C aliphatic aldehyde, a C to C aliphatic ketone or mixtures thereof to produce said neutral oil, and wherein said hydrorefining is at a temperature in the range of 550-750 F.- and a hydrogen partial pressure in the range of 800-3000 p.s.i. and wherein said adsorbent comprises at least 3 lbs/bbl. of a naturally-occuring fullers earth bleaching clay.

5. Process according to claim 4 wherein said naphthenic distillate has a viscosity in the range of 4000-6000 SUS at 100 F., and is substantially free of naphthenic acids, wherein said contacting is at -90 F. in the presence of 0.5 to volumes per volume of distillate of an inert solvent for said distillate, and wherein said hydrorefining is at a temperature in the range of 575 675 F. and a hydrogen partial pressure in the range of 900-1500 p.s.i.

6. A naphthenic cable oil containing 30-50 percent aromatics and having a viscosity in the range of 3000- 8000 SUS at 100 F., an ADF less than 0.0025 in the absence of added oxidation inhibitors, an initial dissipation factor (IDF) less than 0.001, an initial ASTM D1500 color less than 1.5, an aged ASTM color less than 2.0 and a 260 UVA less than 6.0.

7. A naphthenic cable oil according to claim 6-containing 30-40% aromatics, having a viscosity in the range of 4000-6000 SUS at 100 F., a 260 UVA less than 3.0 and having an IDF less than 0.0003 and an ADF less than 0.0015.

8. An electrical cable capable of carrying current at voltages of 500 kv. or greater and containing an insulating fluid comprising the naphthenic cable oil of claim 6.

9. An electrical cable capable of carrying current at voltages of 500 kv. or greater and containing an insulating fluid comprising the naphthenic cable oil of claim 7.

10. Process according to claim 1 wherein said hydrorefining is at a fresh feed LHSV of 0.2-1.0 and recycle LHSV of 2-5, with sulfided nickel-molybdenum oxides as the catalyst, at a temperature below about 750 F. and at a hydrogen partial pressure in the range of 1000- 1500 p.s.i. p

References Cited UNITED STATES PATENTS OTHER REFERENCES Von HippelDielectric Materials and Applications, John Wiley and Sons, London, (1961) pp. 156 to 160.

HERBERT LEVINE, Primary Examiner US. Cl. X.R. 

